Impaired fecal IgA production after treatment with FTY720. (A) Fecal extracts were collected from the reconstituted SCID mice and analyzed for immunoglobulin production by ELISA as described in Figure 6A. Horizontal bars represent the mean. (B) Similarly, mononuclear cells were isolated from small intestinal lamina propria and used for the ELISPOT assay. The error bars are ± SEM (n = 5). (C-D) pIgR expression in epithelial cells (C) and J-chain expression in lamina propria lymphocytes (D) were examined by RT-PCR. Data are representative of 3 independent experiments. (E) SCID mice were adoptively transferred with purified peritoneal B1 or B2 cells and treated with FTY720 as described in Figure 6A. FACS analysis was performed to detect IgA⁺ and IgM⁺ cells in the intestinal lamina propria of mice treated with (right) or without (left) FTY720. Data are representative of 3 independent experiments. (F) Mice were orally immunized with R36A together with cholera toxin and treated with (•) or without (○) FTY720. After 3 days, fecal PC-specific IgA levels were measured by ELISA. The error bars are ± SEM (n = 4). *P < .05.